Regulation of transcription involving selective activation of a small number of genes in individual cells in considered to be a primary mechanism leading to development and differentiation in eukaryotic organisms. Hormonal action whether mediated by secondary factors like cytoplasmic receptors or cyclic AMP also involves selective transcription. Insect development is also under genetic and hormonal control. Two hormones juvenile hormone and ecdysone control the dynamic changes that occur between various stages when entire sets of genes are assumed to be turned "on" or "off" in succession. Since these changes are acquisitions of new functions suited for different kinds of life, the changes are presumably due to the induction or preferential synthesis of new proteins. The precise mechanisms by which these hormones control insect metamorphosis remains to be established. The assumptions behind many of the studies related to hormonal function in insects appear to be (a) There exist different genes (sets) specifying larval, pupal and adult stages and (b) These genes (sets) are turned "on" and "off" in succession by the interaction of the two hormones. The present proposal aims at answering the following questions: 1) Are there different sets of genes corresponding to the different stages of development which are expressed as mRNAs and which are in turn translated into identifiable polypeptide products?; and 2) How does the JH modify or control ecdysone action? These question will be answered by comparing the poly A containing mRNA populations of insect tissues ideally suited for this purpose, at different developmental stages and under varying hormonal treatments as to their (a) capacity to be translated in vitro to identifiable polypeptide components; (b) complexity and abundance of mRNA sequences common to and different from each other; and (c) similarity to RNA transcripts produced in vitro from isolated chromatin. The mRNAs will be translated in the wheat germ cell free system and compared by analyzing the kinetics of hybridization to DNA. Nucleic acid hybridizations will be carried out under two conditions; 1) in DNA excess and 2) in RNA excess. Transcription of isolated chromatin will be carried out with both bacterial and homologous RNA polymerases.